High thermal budget compatible punch through stop integration using doped glass

ABSTRACT

A method of forming a punch through stop region in a fin structure is disclosed. The method may include forming a doped glass layer on a fin structure and forming a masking layer on the doped glass layer. The method may further include removing a portion of the masking layer from an active portion of the fin structure, and removing an exposed portion the doped glass layer that is present on the active portion of the fin structure. A remaining portion of the doped glass layer is present on the isolation portion of the fin structure. Dopant from the doped glass layer may then be diffused into the isolation portion of the fin structure to form the punch through stop region between the active portion of the fin structure and a supporting substrate.

BACKGROUND

Technical Field

The present disclosure relates to semiconductor devices, such assemiconductor devices including fin structures.

Description of the Related Art

The dimensions of semiconductor field effect transistors (FETs) havebeen steadily shrinking over the last thirty years or so, as scaling tosmaller dimensions leads to continuing device performance improvements.Planar FET devices typically have a conducting gate electrode positionedabove a semiconducting channel, and electrically isolated from thechannel by a thin layer of gate oxide. Current through the channel iscontrolled by applying voltage to the conducting gate. With conventionalplanar FET scaling reaching fundamental limits, the semiconductorindustry is looking at more unconventional geometries that willfacilitate continued device performance improvements. One such class ofdevice is a fin field effect transistor (finFET).

SUMMARY

In one aspect, a method of forming a punch through stop (PTS) region ina fin structure is provided that includes forming a doped glass layer ona fin structure, and forming a masking layer on the doped glass layer. Aportion of the masking layer may then be removed from being over anactive portion of the fin structure. A remaining portion of the maskinglayer may be present on the doped glass layer that is present on anisolation portion of the fin structure. In a following step, an exposedportion of the doped glass layer that is present over the active portionof the fin structure is removed. A remaining portion of the doped glasslayer is present on the isolation portion of the fin structure. Dopantfrom the doped glass layer is diffused into the isolation portion of thefin structure to form the punch through stop (PTS) region between theactive portion of the fin structure and a supporting substrate.

In another embodiment, a method of forming a semiconductor device isprovided that includes forming a doped glass layer on a fin structure,and removing a portion the doped glass layer that is present on anactive portion of the fin structure. A remaining portion of the dopedglass layer is present on an isolation portion of the fin structure.Dopant from the doped glass layer may be diffused into the isolationportion of the fin structure to form a punch through stop (PTS) regionbetween the active portion of the fin structure and a supportingsubstrate. A gate structure may be formed on a channel region of theactive portion of the fin structure. Source and drain regions may beformed on the fin structure on opposing sides of the channel region.

In another aspect, a semiconductor device is provided that includes afin structure including an active portion and an isolating portion. Theactive portion of the fin structure includes a channel region and sourceand drain regions on opposing sides of the channel region. The isolatingportion of the fin structure includes a doped punch through stop (PTS)region that is present underlying the channel region and the source anddrain regions of the active portion. The semiconductor device mayfurther include a spacer of doped glass present on the isolation portionof the fin structure. The spacer of doped glass may not be present onthe active portion. A gate structure is present on the channel region ofthe active portion of the fin structure.

BRIEF DESCRIPTION OF DRAWINGS

The following detailed description, given by way of example and notintended to limit the disclosure solely thereto, will best beappreciated in conjunction with the accompanying drawings, wherein likereference numerals denote like elements and parts, in which:

FIG. 1 is a side cross-sectional view that depicts forming at least onefin structure from a bulk semiconductor substrate, in accordance withone embodiment of the present disclosure.

FIG. 2 is a side cross-sectional view depicting forming a doped glasslayer on a fin structure, and forming a masking layer on the doped glasslayer, in accordance with one embodiment of the present disclosure.

FIG. 3 is a side cross-sectional view depicting removing a portion ofthe masking layer from being over an active portion of the finstructure, in which a remaining portion of the masking layer may bepresent on the doped glass layer that is present on an isolation portionof the fin structure, in accordance with one embodiment of the presentdisclosure.

FIG. 4 is a side cross-sectional view depicting removing an exposedportion of the doped glass layer that is present on the active portionof the fin structure, wherein a remaining portion of the doped glasslayer is present on the isolation portion of the fin structure, inaccordance with one embodiment of the present disclosure.

FIG. 5 is a side cross-sectional view depicting forming an isolationregion and applying an anneal process to diffuse dopant from the dopedglass layer into the isolation portion of the fin structure to form thepunch through stop (PTS) region between the active portion of the finstructure and a supporting substrate.

FIG. 6 is a side cross-sectional view depicting forming a gate structureon the channel region portion of the active region of the fin structure.

FIG. 7 is a perspective view depicting forming source and drain regionson the structure depicted in FIG. 6.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely illustrative of the claimed structures and methods that maybe embodied in various forms. In addition, each of the examples given inconnection with the various embodiments are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the methods and structures of the present disclosure. Forpurposes of the description hereinafter, the terms “upper”, “lower”,“right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, andderivatives thereof shall relate to the embodiments of the disclosure,as it is oriented in the drawing figures. The terms “positioned on”means that a first element, such as a first structure, is present on asecond element, such as a second structure, wherein interveningelements, such as an interface structure, e.g. interface layer, may bepresent between the first element and the second element. The term“direct contact” means that a first element, such as a first structure,and a second element, such as a second structure, are connected withoutany intermediary conducting, insulating or semiconductor layers at theinterface of the two elements.

As used herein, “semiconductor device” refers to an intrinsicsemiconductor material that has been doped, that is, into which a dopingagent has been introduced, giving it different electrical propertiesthan the intrinsic semiconductor. Doping involves adding dopant atoms toan intrinsic semiconductor, which changes the electron and hole carrierconcentrations of the intrinsic semiconductor at thermal equilibrium.Dominant carrier concentration in an extrinsic semiconductor determinesthe conductivity type of the semiconductor. A field effect transistor(FET) is a semiconductor device in which output current, i.e.,source-drain current, is controlled by the voltage applied to a gatestructure to the semiconductor device. A field effect transistor hasthree terminals, i.e., gate structure, source region and drain region.As used herein, a “fin structure” refers to a semiconductor material,which is employed as the body of a semiconductor device, in which thegate structure is positioned around the fin structure such that chargeflows down the channel on the two sidewalls of the fin structure andoptionally along the top surface of the fin structure. A FinFET is asemiconductor device that positions the channel region of thesemiconductor device in a fin structure.

In some embodiments, the methods and structures disclosed herein providea punch through stopper (PTS) region for reducing the incidence ofleakage based performance degradation in FinFETs. It has been determinedthat the formation of punch through stopper (PTS) regions formed inFinFETs using prior methods have a number of disadvantages. For example,forming a punch through stopper (PTS) region in a fin structure by ionimplantation produces a high concentration of the dopant for the punchthrough stopper (PTS) region in the at least the channel region of theFinFET. This results in a low mobility of charge carriers in the device,as well as a large variation in threshold voltage (Vt). Further,introducing punch through stopper (PTS) dopant into the channel regionof a fin structure, using any method including diffusion from dopantlayers, results in the same effect as implanting the dopant into thechannel region. The present disclosure provides a means to introducepunch through stopper dopant to the portion of the fin structureunderlying the channel region without introducing high concentrations ofthe punch through stopper (PTS) region dopant into the active region ofthe fin structure, i.e., the channel region and the source and drainregion. More specifically, in some embodiments, the present disclosureprovides a glass layer that is doped with punch through stopper (PTS)dopant that is present only adjacent to the isolation portion of the finstructure. The isolation portion of the fin structure is the portion ofthe fin structure that is present between the active portion of the finstructure and the supporting substrate that the fin structure is engagedto. In some embodiments, by diffusing dopant from the doped glass layerthat is present adjacent to the isolation portion of the fin structureinto the isolation portion of the fin structure, the present disclosureprovides a punch through stopper (PTS) region without introducing a highconcentration of punch through stopper (PTS) dopant to the activeportion of the fin structure. The methods and structures of the presentdisclosure are now discussed with more detail referring to FIGS. 1-7.

FIG. 1 depicts one embodiment of forming at least one fin structure 10from a semiconductor substrate. The at least one fin structure 10 may beformed from a bulk semiconductor substrate 5. The at least one finstructure 10 may be formed using photolithography and etch processes. Inone embodiment, a hard mask 15 is formed on the bulk semiconductorsubstrate 1 prior to etch processing for forming the at least one finstructure 10. For example, a hard mask dielectric layer, such as anitride or oxide material layer, may be blanked deposited atop the bulksemiconductor substrate 1 prior to etching to form the at least one finstructure 10. For example, the hard mask dielectric layer may be blankeddeposited using a deposition process, such as chemical vapor deposition(CVD), e.g., plasma enhanced chemical vapor deposition (PECVD), chemicalsolution deposition, spin on deposition or physical vapor deposition.The hard mask dielectric layer may have a thickness ranging from 2 nm to15 nm. In some examples, the blanket deposited hard mask dielectriclayer may be composed of silicon nitride, e.g., Si₃N₄, siliconoxynitride or silicon oxide.

An etch mask, e.g., photoresist mask, may then be formed on the blanketdeposited hard mask dielectric layer. To provide the photoresist mask, aphotoresist layer is first positioned on the layer of the dielectricmaterial that provides dielectric fin cap. The photoresist layer may beprovided by a blanket layer of photoresist material that is formedutilizing a deposition process such as, for example, chemical vapordeposition, plasma enhanced chemical vapor deposition, evaporation orspin-on coating. The blanket layer of photoresist material is thenpatterned to provide the photoresist mask utilizing a lithographicprocess that may include exposing the photoresist material to a patternof radiation and developing the exposed photoresist material utilizing aresist developer.

The blanket deposited hard mask layer than may be etched using an etchprocess that is selective to at least the photoresist mask, wherein theportion of the blanket deposited hard mask layer protected by thephotoresist mask remain to provide the hard mask 15 and the exposedportions of the blanket deposited hard mask layer are removed. Thephotoresist mask may then be removed.

The bulk semiconductor substrate 1 may then be etched using the hardmask 15 as an etch mask to form the fin structures 10. The etch processfor forming the at least one fin structure 10 may be an anisotropicetch. The term “anisotropic etch process” denotes a material removalprocess in which the etch rate in the direction normal to the surface tobe etched is greater than in the direction parallel to the surface to beetched. The anisotropic etch may include reactive-ion etching (RIE).Other examples of anisotropic etching that can be used at this point ofthe present disclosure include ion beam etching, plasma etching or laserablation. In some embodiments, the etch process for etching the bulksemiconductor substrate 1 and defining the at least one fin structure 10is a timed etch. It is noted that the above description of the etchsequence for forming the fin structures is only one example, and thepresent disclosure is not intended to be limited to only this example.For example, the etch process for forming the at least one fin structure10 may be included within a sidewall image transfer (SIT) process flowin which a mandrel structure is used to form a spacer, in whichfollowing formation of the spacer, the mandrel is removed and the spacercan function as an etch mask.

Still referring to FIG. 1, the etch process may continue until each ofthe fin structures 10 may have a height H₁ ranging from 5 nm to 200 nm.In another embodiment, each of the fin structures 10 has a height H₁ranging from 10 nm to 100 nm. In one example, each of the fin structures10 has a height H₁ ranging from 20 nm to 50 nm. Each of the finstructures 10 may have a width W₁ of less than 15 nm. In anotherembodiment, each of the fin structures 10 has a width W₁ ranging from 3nm to 8 nm. Although one fin structure 10 is depicted in FIG. 1, thepresent disclosure is not limited to only this example. It is noted thatany number of fin structures 10 may be employed in accordance with thepresent disclosure.

In some embodiments, the at least one fin structure 10 may be composedof a type IV semiconductor material or a compound semiconductormaterial. By “type IV semiconductor” it is meant that the semiconductormaterial includes at least one element from Group IVA (i.e., Group 14)of the Periodic Table of Elements. Examples of type IV semiconductormaterials that are suitable for the fin structure include silicon (Si),germanium (Ge), silicon germanium (SiGe), silicon doped with carbon(Si:C), silicon germanium doped with carbon (SiGe:C) and a combinationthereof. A compound semiconductor may be a III-V semiconductor materialor a type II/VI semiconductor material. By “III-V semiconductormaterial” it is meant that the semiconductor material includes at leastone element from Group IIIA (i.e., Group 13) of the Periodic Table ofElements and at least one element from Group VA (i.e., Group 15) of thePeriodic Table of Elements. Examples of compound semiconductor materialsthat are suitable for the fin structures 10 include at least one ofaluminum antimonide (AlSb), aluminum arsenide (AlAs), aluminum nitride(AlN), aluminum phosphide (AlP), gallium arsenide (GaAs), galliumphosphide (GaP), indium antimonide (InSb), indium arsenic (InAs), indiumnitride (InN), indium phosphide (InP), aluminum gallium arsenide(AlGaAs), indium gallium phosphide (InGaP), aluminum indium arsenic(AlInAs), aluminum indium antimonide (AlInSb), gallium arsenide nitride(GaAsN), gallium arsenide antimonide (GaAsSb), aluminum gallium nitride(AlGaN), aluminum gallium phosphide (AlGaP), indium gallium nitride(InGaN), indium arsenide antimonide (InAsSb), indium gallium antimonide(InGaSb), aluminum gallium indium phosphide (AlGaInP), aluminum galliumarsenide phosphide (AlGaAsP), indium gallium arsenide phosphide(InGaAsP), indium arsenide antimonide phosphide (InArSbP), aluminumindium arsenide phosphide (AlInAsP), aluminum gallium arsenide nitride(AlGaAsN), indium gallium arsenide nitride (InGaAsN), indium aluminumarsenide nitride (InAlAsN), gallium arsenide antimonide nitride(GaAsSbN), gallium indium nitride arsenide aluminum antimonide(GaInNAsSb), gallium indium arsenide antimonide phosphide (GaInAsSbP),and combinations thereof. It is noted that in some embodiments, the finstructures 10 are formed from the substrate 1. Therefore, in someembodiments, the fin structure 10 and the supporting substrate 1 havethe same composition.

FIG. 2 depicts one embodiment of forming a doped glass layer 20 on theat least one fin structure 10, and forming a masking layer 25 on thedoped glass layer 20. Each of the doped glass layer 20 and the maskinglayer 25 may be conformal layers. The term “conformal denotes a layerhaving a thickness that does not deviate from greater than or less than30% of an average value for the thickness of the layer. The doped glasslayer 20 may be formed on the sidewalls of the fin structure 10, thesidewalls of the hardmask 15, the upper surface of the hardmask 15 andthe exposed upper surface of the supporting substrate 1. The doped glasslayer 20 may be composed of a doped dielectric material. The dopant ofthe dielectric material for the doped glass layer 20 is selected to havean opposite conductivity type as the conductivity type of the source anddrain regions. The term “conductivity type” means that the dopant iseither a p-type dopant or an n-type dopant. The opposite conductivitytype of a p-type dopant is an n-type dopant, and the oppositeconductivity type of an n-type dopant is a p-type dopant. As usedherein, “p-type” refers to the addition of impurities to an intrinsicsemiconductor that creates deficiencies of valence electrons. Forexample, in a type IV semiconductor material, such as silicon (Si),examples of n-type dopants, i.e., impurities, include but are notlimited to: boron, aluminum, gallium and indium. As used herein,“n-type” refers to the addition of impurities that contributes freeelectrons to an intrinsic semiconductor. For example, in a type IVsemiconductor, such as a silicon including fin structure 10, examples ofn-type dopants, i.e., impurities, include but are not limited toantimony, arsenic and phosphorous.

In some examples, the conductivity type of the source and drain regionsindicates the conductivity type of the device. For example, a p-typeFinFET would have p-type source and drain regions, and an n-type FinFETwould have n-type source and drain regions. The dopant of the dopedglass layer 20 provides the dopant for the punch through stop (PST)region in the isolation portion of the fin structure 10. Therefore, thedopant of the doped glass layer 20 is selected to have an oppositeconductivity as the dopant that provides the conductivity type of theFinFET, e.g., the dopant conductivity of the source and drain region. Byhaving an opposite conductivity type as the conductivity type of theFinFET, the punch through stop (PST) region produces a repulsive fieldunderlying the active portion of the FinFET that obstructs leakage ofcharge carriers out of the active portion of the fin structure 10.

The doped glass layer 20 is typically composed of a silicate glass thatis doped with an n-type or p-type dopant. For example, the selected fromthe group consisting of borosilicateglass (BSG) (p-type silicate glass),phosphosilicate glass (PSG)(n-type silicate glass), and arsenosilicateglass (ASG)(n-type silicate glass). The doped glass layer 20 may bedeposited using chemical vapor deposition (CVD), such as plasma enhancedCVD (PECVD) or metal organic chemical vapor deposition (MOCVD). Thedoped glass layer 20 may also be formed using chemical solutiondeposition or spin on deposition, e.g., spin on glass deposition. Thedopant may be introduced to the doped glass layer in-situ. By “in-situ”it is meant that the dopant e.g., n-type or p-type, that is beingintroduced to the doped glass layer 20 is introduced during thedeposition step that forms the doped glass layer 20. In someembodiments, the thickness of the doped glass layer 20 may range from 2nm to 50 nm. In other embodiments, the thickness of the doped glasslayer ranges from 5 nm to 25 nm.

Following the formation of the doped glass layer 20, the masking layer25 is deposited. The masking layer 25 is composed of a material that maybe etched selectively to the at least the doped glass layer 20. The term“selective” as used to describe a material removal process denotes thatthe rate of material removal for a first material is greater than therate of removal for at least another material of the structure to whichthe material removal process is being applied. In some embodiments, themasking layer 25 may be an oxide, such as silicon oxide, a nitride, suchas silicon nitride, or a silicon oxynitride. In yet other examples, themasking layer 25 can be composed of hafnium oxide, hafnium siliconoxide, hafnium silicon oxynitride, lanthanum oxide, lanthanum aluminumoxide, zirconium oxide, zirconium silicon oxide, zirconium siliconoxynitride, tantalum oxide, titanium oxide, barium strontium titaniumoxide, barium titanium oxide, strontium titanium oxide, yttrium oxide,aluminum oxide, lead scandium tantalum oxide, lead zinc niobate,nitrided hafnium silicate (HfSiON), lanthanum oxide (La₃O₂), lanthanumaluminate (LaAlO₃), zirconium silicate (ZrSiO_(x)) and combinationsthereof. It is noted that the above compositions are only examples ofdielectric compositions that can be suitable for forming the maskinglayer 25, and it is not intended that the present disclosure be limitedto only those examples. Any material that is suitable for selectiveetching relative to at least one of the doped glass layer 20 and the atleast one fin structure 10 is suitable for use with the presentdisclosure.

Referring to FIG. 2, the masking layer 25 may be blanket deposited overthe entirety of the doped glass layer. The masking layer 25 may bedeposited using chemical vapor deposition (CVD), such as plasma enhancedCVD (PECVD) or metal organic chemical vapor deposition (MOCVD). Themasking layer 25 may also be formed using chemical solution depositionor physical vapor deposition. The masking layer 25 may have a thicknessranging from 2 nm to 50 nm. In other embodiments, the thickness of themasking layer 25 ranges from 5 nm to 25 nm.

FIG. 3 depicts removing a portion of the masking layer 25 from an activeportion of the fin structure 10, in which a remaining portion of themasking layer 25 may be present on the doped glass layer 20 that ispresent on an isolation portion of the fin structure 10. The activeportion of the fin structure 10 includes the channel region, the sourceregion and the drain region portions of the fin structure 10. These arethe portions of the fin structure 10 in which the charge carriers aretraveling during functioning of the FinFET. The isolation portion of thefin structure 10 is present between the active portion of the finstructure and the supporting substrate 1, wherein the isolation portionof the fin structure is further processed below to provide the locationof the punch through stopper (PTS) region of the FinFET, which obstructsthe charge carriers from leaking out of the active portion of the finstructure 10.

In some embodiments, the portion of the masking layer 25 that is removedto expose the portion of the doped glass layer 20 that is present on theactive portion of the fin structure 10 is removed using an anisotropicetch, such as reactive ion etch. Reactive Ion Etching (RIE) is a form ofplasma etching in which during etching the surface to be etched isplaced on the RF powered electrode. Moreover, during RIE the surface tobe etched takes on a potential that accelerates the etching speciesextracted from plasma toward the surface, in which the chemical etchingreaction is taking place in the direction normal to the surface. Otherexamples of anisotropic etching that can be used at this point of thepresent disclosure include ion beam etching, plasma etching or laserablation.

In some embodiments, the etch process for removing the masking layer 25from the active portion of the fin structure 10 includes applying ananisotropic etch to remove the laterally orientated surfaces of themasking layer 25 and to recess the vertically orientated surfaces of themasking layer 25 to provide an exposed of the doped glass layer 20 thatis present on the active portion of the fin structure 10. In someembodiments, the anisotropic etch that exposes the portion of the dopedglass layer 20 that is present on the active portion of the finstructure 10 removes the masking layer 25 selectively to the doped glasslayer 20. In some embodiments, the anisotropic etch process that etchesthe masking layer 25 also removes the horizontally orientated portionsof the doped glass layer, such as the portions of the doped glass layer20 present on the upper surface of the hard mask 15 and the horizontallyorientated portions of the doped glass layer 20 that is present on theupper surfaces of the supporting substrate 1, as depicted in FIG. 3.

FIG. 4 depicts one embodiment of removing an exposed portion of thedoped glass layer 20 that is present on the active portion of the finstructure 10, wherein a remaining portion of the doped glass layer 20 ispresent on the isolation portion of the fin structure 10. The etchprocess for removing the exposed portion of the doped glass layer 20 maybe a selective etch process. For example, in one embodiment, a selectiveetch may include an etch chemistry that removes a first materialselectively to a second material by a ratio of 100:1 or greater. In someembodiments, the etch process removes the exposed portions of the dopedglass layer 20 selectively to at least one of the remaining portion ofthe masking layer 25, the fin structure 10, the hardmask 15, and thesupporting substrate 1. Following the selective etch process, aremaining portion of the doped glass layer 20 is only present on thesidewalls of the isolation portion of the fin structure 10. The etchprocess for removing the exposed portion of the doped glass layer 20 maybe an anisotropic etch or an isotropic etch. In some examples, the etchprocess may be a wet chemical etch, reactive ion etch (RIE), plasmaetch, laser etch and combinations thereof. In one example, the etchprocess for removing the exposed portion of the doped glass layer 20 isa wet oxide etch.

FIG. 5 depicts one embodiment of forming an isolation region 35 andapplying an anneal process to diffuse dopant from the doped glass layer20 into the isolation portion of the fin structure 10 to form the punchthrough stop region 30 between the active portion of the fin structure10 and the supporting substrate 1. The isolation region 35 may becomposed of any dielectric material. For example, the isolation region35 may be composed of an oxide, nitride or oxynitride material. In oneexample, when the isolation region 35 is composed of an oxide, the oxidemay be silicon oxide. The dielectric material of the isolation region 35may be formed using a CVD or other like deposition process. Thedielectric of the isolation region 35 may be densified after deposition.For example, the isolation region 35 may be annealed.

The anneal process for densifying the isolation region 35 may alsodiffuse the dopant from the doped glass layer 20 that is present on thesidewalls of the isolation portion of the fin structure 10 into theinterior of the isolation portion of the fin structure 10 to provide thepunch though stop (PST) region 30. The anneal process may be a thermaldiffusion step that can include, but is not limited to, rapid thermalannealing, furnace annealing, laser annealing and combinations thereof.In one embodiment, the thermal diffusion is completed at a firsttemperature ranging from 350° C. to 1000° C. for a time period rangingfrom 1 second to 90 seconds. In another embodiment, the thermalannealing process for forming the punch through stop (PST) region 30 mayinclude a temperature that ranges from 600° C. to 800° C.

The punch through stop (PTS) region dopant may be an n-type or p-typedopant that has an opposite conductivity type as the dopant thatdetermined the conductivity type of the FinFET. For example, the punchthrough stop (PTS) region dopant may be an n-type or p-type dopant thathas an opposite conductivity type as the dopant that dictates theconductivity type of the source and drain region of the FinFET.

The punch through dopant in the punch through stop (PTS) region 30 ofthe isolating portion of the fin structure 10 may be present in aconcentration ranging from 4×10¹⁸ dopants/cm³ to 3×10¹⁹ dopants/cm³. Thechannel region portion of the active portion of the fin structure 10typically has a substantially lower concentration of punch throughdopant. For example, the concentration of punch through stopper dopantthat diffuses into the active portion of the fin structure 10 using themethods described with reference to FIGS. 1-5 is orders of magnitudeless than the concentration of the punch through stopper dopant that ispresent in the channel region of device formed using prior methods, suchas ion implantation.

In some embodiments, using the methods of the present disclosure, i.e.,the methods described with reference to FIGS. 1-5, a tail of dopant maybe present in decreasing concentration extending from the punch throughstopper (PTS) region 30 into the active portion of the fin structure 10.In one embodiment, the concentration of the punch through stopper dopantin the tail may range from a high concentration extending from the punchthrough stopper region to a low concentration, e.g., orders of magnitudelayer, at the upper surface of the active portion of the fin structure10, on which the gate structure is formed. In one example, theconcentration of punch through dopant in the tail will decrease from ahigh concentration of approximately 1×10¹⁸ dopants/cm³ adjacent to thepunch through stopper (PTS) region 30 to a low concentration ofapproximately 1×10¹⁷ dopants/cm³ at the upper surface of the activeportion of the fin structure 10, on which the gate structure is formed.It is noted that the above concentrations are provided for illustrativepurposes only, and are not intended to limit the present disclosure toonly these examples.

FIG. 6 depicts forming a gate structure 40 on the channel region portionof the active region of the fin structure 10. Forming the gate structure40 may begin with recessing the isolation region 35 to expose the activeportion of the fin structure 10. The upper surface of the isolationregion 35 may be recessed using an anisotropic etch, such as reactiveion etch (RIE). The depth by which the isolation region 35 is recessedmay provide a height dimension for the active portion of the finstructure 10.

The gate structure 40 typically includes at least a gate dielectric 41that is present on the channel region of active portion the finstructure 10, and a gate electrode 42 that is present on the gatedielectric 41. In one embodiment, the at least one gate dielectric layer41 includes, but is not limited to, an oxide, nitride, oxynitride and/orsilicates including metal silicates, aluminates, titanates and nitrides.In one example, when the at least one gate dielectric layer 41 iscomprised of an oxide, the oxide may be selected from the groupincluding, but not limited to, SiO₂, HfO₂, ZrO₂, Al₂O₃, TiO₂, La₂O₃,SrTiO₃, LaAlO₃, Y₂O₃ and mixture thereof. The physical thickness of theat least one gate dielectric layer 41 may vary, but typically, the atleast one gate dielectric layer 41 has a thickness from 1 nm to 10 nm.In another embodiment, the at least one gate dielectric layer 41 has athickness from 1 nm to 3 nm.

The conductive material of the gate electrode 42 may comprisepolysilicon, SiGe, a silicide, a metal or a metal-silicon-nitride suchas Ta—Si—N. Examples of metals that can be used as the gate electrode 42include, but are not limited to, Al, W, Cu, and Ti or other likeconductive metals. The layer of conductive material for the gateelectrode 42 may be doped or undoped. If doped, an in-situ dopingdeposition process may be employed. Alternatively, a doped conductivematerial can be formed by deposition, ion implantation and annealing. Inyet another embodiment, when the fin structure 10 is being employed in ap-FinFET, the gate electrode may be composed of a p-type work functionmetal layer. As used herein, a “p-type work function metal layer” is ametal layer that effectuates a p-type threshold voltage shift. In oneembodiment, the work function of the p-type work function metal layerranges from 4.9 eV to 5.2 eV. In one embodiment, the p-type workfunction metal layer may be composed of titanium and theirnitrided/carbide. In one embodiment, the p-type work function metallayer is composed of titanium nitride (TiN). The p-type work functionmetal layer may also be composed of TiAlN, Ru, Pt, Mo, Co and alloys andcombinations thereof.

In yet another embodiment, when the fin structure 10 is being employedin an n-FinFET, the gate electrode 42 may include an n-type workfunction metal layer. An “n-type work function metal layer” is a metallayer that effectuates an n-type threshold voltage shift. In oneembodiment, the work function of the n-type work function metal layerranges from 4.1 eV to 4.3 eV. In some embodiments, the n-type workfunction metal layer is composed of at least one of TiAl, TanN, TiN,HfN, HfSi, or combinations thereof.

The gate structure 40 may be formed by using a deposition method, suchas a chemical vapor deposition method and/or a physical vapor deposition(PVD), to deposit the material layers for the at least one gatedielectric layer 41 and the at least one gate electrode 42 followed byphotolithography and etch processing.

In some embodiments, a gate sidewall spacer 43 can be formed on thesidewall of the gate structure 40, as depicted in FIG. 7. In oneembodiment, the gate sidewall spacer 43 may be formed by using a blanketlayer deposition process, such as CVD, and an anisotropic etchbackmethod. The gate sidewall spacer 43 may have a width ranging from 2.0 nmto 15.0 nm, and may be composed of a dielectric, such as a nitride,oxide, oxynitride, or a combination thereof.

FIG. 7 depicts one embodiment of forming source and drain regions on thesource and drain region portions of the fin structure 10 that arepresent on opposing sides of the fin structure's channel region. Thesource and drain regions, as well as the channel region, are formed inthe active portion of the fin structure 10, which is separated from thesupporting substrate 1 by the isolating portion of the fin structure 10.Although FIG. 7 is a perspective view, that only depicts one of thesource and drain regions, the other of the source and drain regions ispresent on the opposing side of the gate structure 40.

The source and drain regions typically include an epitaxialsemiconductor material 50 that is formed on the source and drain regionportions of the active portion of the fin structure 10. The terms“epitaxial growth and/or deposition” means the growth of a semiconductormaterial on a deposition surface of a semiconductor material, in whichthe semiconductor material being grown has substantially the samecrystalline characteristics as the semiconductor material of thedeposition surface. The term “epitaxial semiconductor material” denotesa material that is formed using epitaxial growth. In some embodiments,when the chemical reactants are controlled and the system parameters setcorrectly, the depositing atoms arrive at the deposition surface withsufficient energy to move around on the surface and orient themselves tothe crystal arrangement of the atoms of the deposition surface. Thus, insome examples, an epitaxial film deposited on a {100} crystal surfacewill take on a {100} orientation. The epitaxial deposition process mayemploy a chemical vapor deposition apparatus.

The epitaxial semiconductor material 50 for the source and drain regionsmay be a type IV semiconductor, such as silicon (Si), silicon germanium(SiGe), germanium (Ge), silicon doped with carbon (Si:C), or theepitaxial semiconductor material 50 for the source and drain regions maybe at type III-V compound semiconductor material, such as galliumarsenide (GaAs). The epitaxial semiconductor material 50 may be doped tothe conductivity type of the source and drain region. For example, ifthe semiconductor device is an n-type FinFET, the epitaxialsemiconductor material 50 that is present on the source and drain regionportions of the fin structure 10 is doped to an n-type conductivity; andif the semiconductor device is a p-type FinFET, the epitaxialsemiconductor material 50 that is present on the source and drain regionportions of the fin structure 10 is doped to a p-type conductivity. Then-type or p-type dopant in the source and drain regions may also bereferred to a charge carrier type dopant.

The dopant may be introduced to the epitaxial semiconductor material 50using in-situ doping. The term “in-situ” as used to describe the dopantthat provides the conductivity type of the source and drainsemiconductor material means that the dopant, e.g., p-type dopant, thatdictates the conductivity type of the epitaxially formed in situ dopedsource and drain semiconductor material is introduced during the processstep, e.g., epitaxial deposition, which forms the in situ doped sourceand drain semiconductor material. In some embodiments, extension sourceand drain regions may be formed in the source and drain region portionsof the active portion of the fin structure 10 by thermally diffusing thedopant from the epitaxial semiconductor material 50 into the activeportion of the fin structures 10. In some embodiments, the chargecarrier type dopant in said source and drain region is present in aconcentration ranging from 1×10²⁰ dopants/cm³ to 2×10²⁰ dopants/cm³.

It is noted that in the above examples, a gate first process has beendescribed for forming the gate structure 40. The methods and structuresof the present disclosure are not limited to only this process flow, asgate last processing is also suitable for use with the presentdisclosure. A gate last process can include forming a replacement gatestructure on the channel portion of the fin structures, forming a spaceron the sidewall of the replacement gate structure, forming source anddrain regions on opposing sides of the replacement gate structure,removing the replacement gate structure, and forming a functional gatestructure in the space once occupied by the replacement gate structure.The replacement gate structure can include sacrificial material thatdefines the geometry of a later formed functional gate structure thatfunctions to switch the semiconductor device from an “on” to “off”state, and vice versa. A process sequence employing a replacement gatestructure may be referred to as a “gate last” process sequence. Bothgate first and gate last process sequences are applicable to the presentdisclosure.

In one embodiment, the present disclosure provides a semiconductordevice, e.g., FinFET semiconductor device, that includes a fin structure10 including an active portion and an isolating portion. The activeportion of the fin structure 10 includes a channel region and source anddrain regions (including in situ doped epitaxial semiconductor material50) on opposing sides of the channel region. The isolating portion ofthe fin structure 10 includes a doped punch through stop (PTS) region 30that is present underlying the channel region and the source and drainregions of the active portion. A spacer of doped glass 20 present on theisolation portion of the fin structure 10, wherein the spacer of dopedglass is not present on the active portion of the fin structure 10. Thespacer of doped glass 20 is a remaining portion of the doped glass layer20 that has been described above with reference to FIGS. 1-5. A maskinglayer 25 may be present on the spacer of doped glass 20, in which aheight of the masking layer 25 is generally equal to a height of thespacer of doped glass 20. The spacer of doped glass 20 and the maskinglayer 25 may be embedded within the isolation region 35. A gatestructure 40 present on the channel region of the active portion of thefin structure 10. Source and drain regions are doped to a firstconductivity type and the punch through stopper (PTS) region 30 is dopedto a second conductivity type, said second conductivity type beingopposite the first conductivity type. In one example, the charge carriertype dopant in the source and drain region may be present in aconcentration ranging from 1×10²⁰ dopants/cm³ to 2×10²⁰ dopants/cm³; andthe dopant of the doped punch through stop region in the isolatingportion of the fin structure 10 may be present in a concentrationranging from 4×10¹⁸ dopants/cm³ to 3×10¹⁹ dopants/cm³. In someembodiments, a tail of punch through stopper (PTS) dopant may be presentin the active portion of the fin structure 10 extending away from thepunch through stopper (PTS) region 30 that is present in the isolationportion of the fin structure. The concentration of punch through dopantin the tail can range from approximately 1×10¹⁷ dopants/cm³ toapproximately 1×10¹⁸ dopants/cm³.

Methods as described herein may be used in the fabrication of integratedcircuit chips. The resulting integrated circuit chips can be distributedby the fabricator in raw wafer form (that is, as a single wafer that hasmultiple unpackaged chips), as a bare die, or in a packaged form. In thelatter case the chip is mounted in a single chip package (such as aplastic carrier, with leads that are affixed to a motherboard or otherhigher level carrier) or in a multichip package (such as a ceramiccarrier that has either or both surface interconnections or buriedinterconnections). In any case the chip is then integrated with otherchips, discrete circuit elements, and/or other signal processing devicesas part of either (a) an intermediate product, such as a motherboard, or(b) an end product. The end product can be any product that includesintegrated circuit chips, ranging from toys and other low-endapplications to advanced computer products having a display, a keyboardor other input device, and a central processor.

While the methods and structures of the present disclosure have beenparticularly shown and described with respect to preferred embodimentsthereof, it will be understood by those skilled in the art that theforegoing and other changes in forms and details may be made withoutdeparting from the spirit and scope of the present disclosure. It istherefore intended that the present disclosure not be limited to theexact forms and details described and illustrated, but fall within thescope of the appended claims.

What is claimed is:
 1. A method of forming a punch through stop regionin a fin structure comprising: forming a doped glass layer on a finstructure; forming a masking layer on the doped glass layer; removing aportion of the masking layer that is present over an active portion ofthe fin structure, wherein a remaining portion of the masking layer ispresent on the doped glass layer that is present on an isolation portionof the fin structure; removing an exposed vertically orientated portionof the doped glass layer that is present on the active portion of thefin structure and removing horizontal portions of the doped glass layerthat are not in direct contact with a sidewall of the fin structure, thehorizontal portions of the doped glass layer being removed extendingover an underlying supporting substrate for the fin structure, wherein aremaining portion of the doped glass layer is present on the isolationportion of the fin structure; and diffusing dopant from the doped glasslayer into the isolation portion of the fin structure to form the punchthrough stop region of dopant extending from the active portion of thefin structure to the underlying supporting substrate.
 2. The method ofclaim 1, wherein the fin structure is formed from a bulk semiconductorsubstrate, a surface of the bulk semiconductor substrate being etched toform the fin structure, wherein a remaining portion of the bulksemiconductor substrate provide the supporting substrate.
 3. The methodof claim 2, wherein etching the bulk semiconductor substrate to form thefin structure comprises: forming a hard mask layer on a surface of thebulk semiconductor substrate; patterning the hard mask layer to providea hard mask; and etching the bulk semiconductor substrate selectively tothe hard mask.
 4. The method of claim 1, wherein forming the doped glasslayer comprises depositing a conformal layer on sidewalls and an uppersurface of the fin structure.
 5. The method of claim 4, wherein thedoped glass layer comprises an n-type or p-type doped silicate glass. 6.The method of claim 4, wherein forming the masking layer comprisesdepositing a conformal layer, the masking layer comprises a compositionthat is etched selectively to at least the hard mask.
 7. The method ofclaim 6, wherein said removing the masking layer from an active portionof the fin structure comprises: applying an anisotropic etch to removethe laterally orientated surfaces of the masking layer and to recess thevertically orientated surfaces of the masking layer to provide saidexposed portion of the doped glass layer that is present on the activeportion of the fin structure; and removing the exposed portion of thedoped glass layer with an isotropic etch.
 8. The method of claim 7,wherein diffusing dopant from the doped glass layer into the isolationportion of the fin structure to form the punch through stop regioncomprises annealing.